The frequency measurement platforms are constructed to measure and obtain the power frequency in Hubei province and Guizhou province respectively. The results show that the frequency distribution characteristics of the two places are similar, which have certain differences with the existing conclusions. The main causes of such frequency distribution are automatic generation control (AGC) non-linear strategy and the load fluctuation characteristics of limited bandwidth. The same frequency distribution with the practical measurement results is presented through simulation considering the above causes. The applying conditions of control performance standard (CPS) is discussed, and the conclusion that the applying condition of CPS2 is large sampling is drawn, that is the CPS2 calculation interval should be long enough.